1. Field of the Invention
The present invention relates to an electronic timepiece with a wireless information function, and more particularly to a radio-controlled timepiece.
2. Description of the Related Art
An electronic timepiece with a wireless communication function enabling the timepiece to receive an RF signal and perform a specified operation based on information contained in the received signal is known from the prior art. One such timepiece is a radio-controlled timepiece having an antenna for receiving a standard radio signal carrying time information, and adjusting the time based on the time information received by the antenna. See, for example, Japanese laid-open patent application nos. H8-285960, 2000-105285 and 2001-33571 (hereinafter referred to as ref. 1, ref. 2 and ref. 3, respectively).
A configuration having an antenna assembled in the leather band of a wristwatch and connected to the watch body through a connection terminal formed in the band is provided in ref. 1. Because the antenna is not disposed in the watch body with this configuration, the watch body can be made smaller and signal reception by the antenna can be isolated from the effects of metal parts in the watch body.
The configuration provided in ref. 2 has an antenna disposed in a groove formed on the inside circumference of the case, which is made from a non-metallic material. Because the case is not metal, the standard radio signal is not blocked by the case and signal reception by the antenna is good.
The configuration provided in ref. 3 has a spacer ring made from a non-conductive material disposed inside a metal case, and the antenna is located on the inside of this spacer ring and separated by the spacer ring a specific distance from the case. By separating the antenna this specific distance from the case, signals can be received by the antenna with good reception without the case blocking the signal, and an appearance of high quality can be achieved because the case is made of metal.
One problem with the radio-controlled timepiece in ref. 1, however, is that it is difficult to make the electrical connection between the band and watch body, and the replacement cost of the band is high because assembling the antenna inside the band makes the band expensive. A further problem is that flexing the band increases the likelihood of damage to the assembled antenna.
With the radio-controlled timepiece in ref. 2, the case is limited to non-metallic materials so that signals are not blocked by the case. The problem here is that significant limitations are imposed on the design and appearance by the inability to use a case made of metal.
The problem with separating the antenna and case sufficiently to prevent any effect on signal reception as in the radio-controlled timepiece in ref. 3 is that the watch becomes extremely large. Furthermore, if the case and antenna are proximally disposed, the standard radio signal is blocked by the case, and reception of the standard radio signal by the antenna is not good.
Also known from the literature (PCT published application no. WO 97/21153 and Japanese laid-open patent application no. H11-223684, hereinafter ref. 4 and ref. 5, respectively) are radio-controlled timepieces having an antenna for receiving a standard time signal containing time information and adjusting the time based on the time information received by the antenna, and having photoelectric means for generating electricity from incident light.
This photoelectric means is composed of a photoelectric device with a photoelectric generating function, and a support base for supporting the photoelectric device. The photoelectric device has a transparent conductive film as the electrode layer, and the support base is a metal substrate of stainless steel, for example.
Because the standard time signal could be blocked by the conductive film and support base, an arrangement in which the photoelectric device does not block the standard time signal before it reaches the antenna is required. When the photoelectric means is disposed over the dial as shown in FIG. 3 or FIG. 5 of ref. 4, for example, the antenna must be located externally to the case so that the photoelectric means and antenna do not overlap.
However, if as proposed in ref. 4 and ref. 5, the photoelectric means and antenna cannot be stacked, the timepiece becomes quite large. The problem with this is that it is not compatible with small, portable timepieces such as wristwatches.
On the other hand, if the antenna is located inside the case, the case must be made from a non-conductive and non-magnetic material so that radio signals are not blocked by the case. In other words, a metal case cannot be used, and it becomes difficult to impart a feeling of high quality.
It should be noted that if the photoelectric means and antenna are small, they can be disposed to mutually non-interfering positions, but the problem here is that if the photoelectric means is small, the light-receiving area is small and electrical generating performance drops. A further problem is that the reception performance of the antenna drops if the antenna is small.
An aesthetically pleasing design is desired in timepieces, and an appearance befitting a luxury accessory is essential for wristwatches in particular. One problem, therefore, is that a metallic appearance and compact design are needed. Another problem is that reception by the antenna must be good in a radio-controlled timepiece or other electronic timepiece with wireless information function.
However, if a metal case is used to provide a high quality feel, and the design is small and compact, signals cannot be received by the antenna with good reception.
The related art described above does not simultaneously address the need for good signal reception by the antenna and an improved appearance, and there is therefore a need for an electronic timepiece with a wireless information function that features both good signal reception and an aesthetically pleasing appearance.